## Clinical Features and Laboratory Findings of Dengue, Chikungunya, and Zika ### Correct Statements **Key Point:** Dengue fever presents with a characteristic biphasic fever pattern ('saddle-back' fever), with an initial febrile phase followed by a brief afebrile period and then recrudescence of fever. Laboratory findings include thrombocytopenia, elevated transaminases (ALT > AST), and leukopenia. [cite:Harrison 21e Ch 189] **Key Point:** Chikungunya causes severe, debilitating arthralgia that is the hallmark of the disease. The arthralgia typically affects small joints (hands, feet, wrists, ankles) and can persist for months to years, sometimes evolving into chronic arthritis. The name 'chikungunya' means 'that which bends up' in Swahili, referring to the joint symptoms. [cite:Park 26e Ch 25] **Key Point:** Dengue hemorrhagic fever (DHF) is a severe manifestation occurring predominantly during secondary infection with a heterologous dengue serotype. It is characterized by plasma leakage leading to hemoconcentration, thrombocytopenia, and hemorrhagic manifestations. This is explained by antibody-dependent enhancement (ADE). [cite:Harrison 21e Ch 189] ### The Incorrect Statement **High-Yield:** Zika virus infection does NOT typically present with arthralgia as a predominant feature. Zika presents with a mild febrile illness characterized by: - Maculopapular rash (often starting on face and spreading to trunk and limbs) - Mild fever - Conjunctivitis (non-purulent) - Myalgia and headache - Arthralgia is MILD and NOT the predominant feature In contrast, chikungunya is dominated by severe, debilitating arthralgia. This distinction is clinically important for differential diagnosis. **Warning:** A common exam trap is confusing the arthralgia patterns of chikungunya (severe, persistent) with Zika (mild, transient). The predominant feature of Zika is the rash and constitutional symptoms, not joint pain. ### Clinical Comparison Table | Feature | Dengue | Chikungunya | Zika | |---------|--------|-------------|------| | Fever pattern | Biphasic ('saddle-back') | Sustained, high fever | Mild fever | | Rash | Maculopapular, centripetal | Maculopapular | Maculopapular, prominent | | Arthralgia/Arthritis | Mild to moderate | **Severe, debilitating** | **Mild** | | Conjunctivitis | Uncommon | Uncommon | **Common** | | Thrombocytopenia | Yes (hallmark) | Mild | Rare | | Elevated transaminases | Yes (ALT > AST) | Mild elevation | Mild elevation | | Chronic sequelae | Rare | Chronic arthritis (common) | Congenital abnormalities | | Incubation | 3–14 days | 2–12 days | 2–14 days | ### Mnemonic for Distinguishing Features **Mnemonic: "DeChi-Z" (Dengue, Chikungunya, Zika)** - **D**engue: **D**ownward fever (biphasic), **D**ropped platelets - **Chi**kungunya: **Chi**ef complaint = joints (arthralgia) - **Z**ika: **Z**ero arthralgia (minimal), **Z**ygote affected (congenital)
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.